首页 | 本学科首页   官方微博 | 高级检索  
文章检索
  按 检索   检索词:      
出版年份:   被引次数:   他引次数: 提示:输入*表示无穷大
  收费全文   17258篇
  免费   2024篇
  国内免费   889篇
电工技术   1640篇
技术理论   3篇
综合类   1595篇
化学工业   986篇
金属工艺   289篇
机械仪表   581篇
建筑科学   2603篇
矿业工程   732篇
能源动力   1056篇
轻工业   1570篇
水利工程   1587篇
石油天然气   695篇
武器工业   341篇
无线电   934篇
一般工业技术   1451篇
冶金工业   1129篇
原子能技术   329篇
自动化技术   2650篇
  2024年   109篇
  2023年   321篇
  2022年   582篇
  2021年   739篇
  2020年   709篇
  2019年   600篇
  2018年   641篇
  2017年   638篇
  2016年   897篇
  2015年   786篇
  2014年   1278篇
  2013年   1555篇
  2012年   1281篇
  2011年   1495篇
  2010年   1115篇
  2009年   1051篇
  2008年   943篇
  2007年   1023篇
  2006年   926篇
  2005年   719篇
  2004年   550篇
  2003年   448篇
  2002年   371篇
  2001年   264篇
  2000年   192篇
  1999年   155篇
  1998年   140篇
  1997年   93篇
  1996年   95篇
  1995年   64篇
  1994年   67篇
  1993年   46篇
  1992年   27篇
  1991年   26篇
  1990年   25篇
  1989年   26篇
  1988年   28篇
  1987年   20篇
  1986年   18篇
  1985年   10篇
  1984年   14篇
  1983年   9篇
  1982年   8篇
  1981年   6篇
  1980年   9篇
  1979年   4篇
  1971年   3篇
  1965年   14篇
  1961年   3篇
  1959年   4篇
排序方式: 共有10000条查询结果,搜索用时 531 毫秒
21.
A telephone survey was carried out on 13,486 randomly selected households located in the Abruzzo region (central Italy). Three questionnaires were specifically designed in relation to three different groups of foods (Meat and meat products, Fishery products, Fruit and vegetables). Questions were mainly focused on the amount and number of purchases, type of retailer, and home food handling practices with respect to the week prior to the interview. Data were classified according to a multilingual thesaurus system (LanguaL). Results allowed to estimate domestic purchases (in kg) per capita for different food categories. The category “Red meat/Cattle” accounted for a large part of purchases in the “meat and meat products” group (10.9 kg per capita/year; 32.2% of purchases in the group) while the category “Fish or related organism/Fish” was the most purchased in the “fishery products” group (6.9 kg per capita/year; 63.3%). The aggregation of more detailed characteristics enabled the identification of popular categories of foods, such as “Red meat/Cattle/Divided into pieces” (25% of the “meat and meat products” group). Significant differences (p < 0.05) were found between the four different provinces (L'Aquila, Chieti, Pescara and Teramo) with respect to “Poultry/Chicken” and “Red meat/Cattle” categories. Householders were also asked about post-purchase food handling practices that might be hazardous to food safety. More than 20% of those surveyed stated that they thawed frozen meat at room temperature. The degree of doneness after cooking of different food categories was generally high: over 90% of products purchased in the majority of meat and fish categories were properly cooked. However a noticeable proportion of householders (about 15%) reported medium or rare cooking of “Red meat/Cattle” and “Red meat/Swine”. Differences (p < 0.05) were also found between consumers of different ages, with people over 65 years old being more prone to freeze meat and cook it thoroughly.The survey was carried out in a specific geographic area and on a statistically significant sample of households, thus allowing a collection of data on domestic habits relating to food purchases and home food handling practices. This information should be included in the framework of quantitative microbial risk assessment (QMRA) models as a measure of the actual exposure of consumers to pathogenic microorganism. The LanguaL system also proved to be a practical language-independent method useful not only to identify and describe food items but also to classify them according to specific food safety characteristics.  相似文献   
22.
The standardization data for the California Verbal Learning Test-Second Edition (CVLT-II; D. C. Delis, J. H. Kramer, E. Kaplan, & B. A. Ober, 2000) were used to evaluate the base rate of 6 specific discrepancies between various key variables. The results indicated that CVLT-II performance discrepancies should equal or exceed 1 or 1.5 z score points (depending on the individual comparison) in the hypothesized direction to be considered potentially unusual. However, because about 1 in 3 persons in the standardization sample displayed at least 1 such large discrepancy, it is concluded that these base rates should be viewed only as a starting point for interpretation. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
23.
Currently, ethnic and racial minority individuals represent a large proportion of the U.S. population, and researchers expect that they will represent the majority of the population by 2050. This shift in U.S. demographics calls for a greater awareness and integration of cultural issues into the assessment and treatment of ethnically and linguistically diverse clients. This article examines the unique beliefs and manifestations of illnesses among Haitians in connection with the American Psychological Association's (APA, 2002) Multicultural Guidelines. The authors use a common culture-bound syndrome, Séizisman, to illustrate the cultural beliefs, assessment, and treatment of illnesses among Haitians. In so doing, they demonstrate how to incorporate the APA Multicultural Guidelines into treatment with clients of diverse cultural and racial backgrounds. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
24.
通过大量野外工程地质勘察与测试工作,在此基础上给出了横泉水库供水发电洞的工程地质分析与评价,从而使该水库的施工有了充分的理论依据。  相似文献   
25.
管道风险管理方法研究   总被引:6,自引:0,他引:6  
按照管道风险管理的流程分别对管道风险评价、风险控制和决策支持、效能测试和响应进行了论述。针对目前国内管道行业的情况,提出了进行管道风险评价的有效方法及维护措施。着重介绍了国外管道风险可接受标准的情况,作为国内制定管道风险评价标准的参考。  相似文献   
26.
低勘探程度区域油气资源评价方法   总被引:5,自引:1,他引:4  
目前中国油气资源勘探和开发面临后备可采储量不足,低勘探程度区域受到重视。为了提高低勘探程度区域的资源评价精度,在前人评价的基础上,通过研究并利用勘探程度较高区域的资源评价结果,求准低勘探程度区域的油气聚集量,进而模拟求出其烃排聚系数、储量密度系数、单储系数和单生系数等关键参数,提出了利用练台地质推断法对低勘探程度区域进行评价,并对该方法评价的风险进行了分析。综合地质推断法的成果更能准确反映一个盆地、坳(凹)陷或区带的油气潜力及其分布特征。  相似文献   
27.
应用API 581对输气站场进行定量风险评价   总被引:3,自引:0,他引:3  
目前专门针对输气站场的风险评价方法还不多,现有的手段也只是根据国家法律法规得出定性的评价结果,然后按照评价结果对照得出整改方案。为此,对输气站场的定量风险评价工作提出了一套新方法,得到了定量的和更加客观的风险排序,为管道站场的完整性管理工作提供了有力的支持;并以陕京输气管道榆林压气站为例,应用美国石油学会标准API 581(基于风险检测的基本源文件)对站内设施进行了风险评价,计算了站内设备和管线的失效后果、失效概率,得到了定量风险值,进而分析了风险值产生差异的原因。最后,针对我国输气管道风险评估工作提出了看法和建议。  相似文献   
28.
基于改进模糊综合评价法的水利工程社会评价研究   总被引:1,自引:0,他引:1  
钟姗姗 《水利科技与经济》2006,12(2):114-115,120
通过对水利工程社会评价及模糊综合评价法的介绍,讨论了模糊层次分析法中的一致性检验问题,并采用改进的模糊综合评价法对江垭水利枢纽工程进行社会评价,得到综合评价结果。  相似文献   
29.
基于ISO/IEC17799标准建立了一个综合的信息系统风险分析框架,并运用模糊多准则决策(FMCDM)方法计算信息安全风险,根据风险等级矩阵(RLM)对信息资产风险进行级别划分,最终建立评估信息资产相关风险的完整模型。  相似文献   
30.
The authors reanalyzed assessment center (AC) multitrait-multimethod (MTMM) matrices containing correlations among postexercise dimension ratings (PEDRs) reported by F. Lievens and J. M. Conway (2001). Unlike F. Lievens and J. M. Conway, who used a correlated dimension-correlated uniqueness model, we used a different set of confirmatory-factor-analysis-based models (1-dimension-correlated Exercise and 1-dimension-correlated uniqueness models) to estimate dimension and exercise variance components in AC PEDRs. Results of reanalyses suggest that, consistent with previous narrative reviews, exercise variance components dominate over dimension variance components after all. Implications for AC construct validity and possible redirections of research on the validity of ACs are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)  相似文献   
设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号